Power generators used in electrosurgical procedures deliver electrical energy to an electrosurgical tool for operating on the tissue of a patient. An active electrode of the tool, connected to the power generator, concentrates the delivery of the electrical energy to a relatively small region of tissue of the patient. The electrical energy typically includes energy in the radio frequency (RF) band. The concentration of electrical energy facilitates cutting or coagulation of the tissue of the patient. During typical operation of a monopolar electrosurgical device, an alternating electrical current from the generator flows from an active electrode to a return electrode by passing through the tissue and bodily fluids of a patient.
During an electrosurgical operation, different tissue types may be encountered, such as, for example, fat, connective, glandular and vascular tissues. Connective, glandular and vascular tissues can have similar characteristics in the way they react to electrical energy, specifically, they have similar characteristics of electrical impedance. Fat however, has significantly different electrical response characteristics. In particular, fat presents a higher impedance to the flow of electrical current than do the other types of tissues. The tissue of certain anatomical portions, or regions, of a patient's body may be largely heterogeneous on a macroscopic scale, such as on a scale commensurate with that of an electrosurgical cutting tool. For example, breast tissue has this heterogeneous property and can be made up of all the tissue types discussed above, i.e., fatty, glandular, connective and vascular tissues. The variations in electrical impedance exhibited by these various tissue types can be problematic when attempting to perform electrosurgical cutting in such heterogeneous, or non-homogeneous, tissue.
In a typical electrosurgical procedure, the amount of electrical energy delivered by a power generator must be carefully controlled. If insufficient power is delivered by the power generator, the tissue cutting of the electrosurgical procedure will be inhibited. If more power than necessary is delivered by the power generator there may excessive, and unnecessary, collateral tissue damage making it more difficult to perform a histology on a sample and thereby decreasing the ability of a pathologist to diagnosis the sample, as well as resulting in a more difficult recovery by the patient in addition to other sequela. Using a regulated power generator helps control and stabilize the electrical energy delivered into the patient's tissue. However, due to the different electrical response characteristics of the various tissue types that may be present, the energy coupled into the tissue may vary even if the power generator is regulated. Generally, typical RF power generators experience difficulty in cutting through fatty non-homogeneous tissue because of the non-homogeneous tissue types that are typically encountered.
In addition, typical RF power generators are only effective with tools having small cutting surfaces. Thus, during an electrosurgical procedure, if fat is encountered, a surgeon must perform surgical cuts by “feathering”, making repetitive shallow cuts with countertraction over the same area to attain a desired depth of cut. In addition, because typical power generators are only effective for tools with small cutting surfaces, the types of tools available to a surgeon during electrosurgery are limited.
There is a need in the art for improved electrosurgical RF power generators that can be used with electrosurgical tools that encounter non-homogeneous tissue, such as, for example, breast biopsy instruments. Electrosurgical tools, such as electrosurgical breast biopsy instruments, can present varying load requirements to an electrosurgical power generator than typical electrosurgical tools, due to the heterogeneous nature of the tissue they are used to cut or coagulate.
From the discussion above, it should be apparent that there is a need for an electrosurgical power generator used in electrosurgical procedures that will more effectively couple electrical energy to different types of tissue, in particular heterogeneous tissue that includes fat tissue. In addition, there is a need for a power generator that works effectively with large cutting surfaces, thereby expanding the types of tools that are available for electrosurgery.
The present invention satisfies these and other needs.